1. Field of Invention
This invention relates to projectiles with hemispherical points that are used in firearms.
2. Description of Prior Art
Revolvers, semi-automatic pistols, automatic machine pistols, submachine guns, small arms using caseless ammunition, shotguns using slugs, penetrating warheads, mortars, missiles, field artillery, and other weapons utilize ammunition with a hemispherical tip profile.
In 1861, when the first centerfire cartridge was patented in England, the projectile's tip profile was essentially hemispherical. In the nearly 150 subsequent years, many attempts have been made to stabilize bullets that have a hemispherical forward profile. With the invention of the jacketed firearms projectile in 1875 and the more recent efforts at balanced projectile loads, the accuracy of hemispherical tip profile ammunition improved.
Still, the two major problems of lack of accuracy and loss of velocity due to turbulence with hemispherical tip profile ammunition have been only partially solved. Hemispherical tip profile ammunition historically underperforms rifle or pointed ammunition due to its aerodynamic inferiority. A typical hemispherical projectile is shown in FIG. 1.
Several patents deal with the use of recessed regions or “dimples” to aid aerodynamic characteristics of projectiles and increase the sustained velocity or accuracy of a projectile object, notably U.S. Pat. No. 4,142,727 to Shaw et al. (1979), U.S. Pat. No. 4,560,168 to Aoyama (1985), and U.S. Pat. No. 5,106,096 to Dunn (1992). Dimples or recessed regions that are numerous and arranged in very specific geometric patterns are discussed in U.S. Pat. No. 6,705,959 to Morgan, et al. (2004). U.S. Pat. No. 6,706,332 to Lutz, et al. discusses methods such as those including using recessed regions to enhance aerodynamic performance of a projectile and then coating regions of the projectile in order to further enhance aerodynamic performance. Recessed regions or dimples in the leading surfaces of a projectile are separate and significantly different in design from voids enclosed within the projectile's body, such as are described in U.S. Pat. No. 6,694,888 to Jopson and Davis (2004) and others. Of course, these patents have adapted their teachings to the specific products disclosed therein.
Many types of ammunition that may improve the aerodynamics of small arms munitions through recessed regions have been proposed, for example, in U.S. Pat. No. 1,149,679 to Parker (1915), U.S. Pat. No. 4,164,904 to Laviolette (1979), and U.S. Pat. No. 4,301,736 to Flatau et al. (1981), but these tend to focus on the concept of one or a small number of deeply recessed regions that make the projectile essentially hollow as a method for reducing aerodynamic resistance. Many patents which do not propose a hollow projectile still often focus on a single deep cavity such as is disclosed in U.S. Pat. No. 5,092,246 to Huerta (1992). U.S. Pat. No. 5,200,573 to Blood (1993) refers to firearm projectiles but also refers to machining cavities into the mold used to cast the projectile and to rolling, swaging, or stamping cavities into the surface of the projectile, all of which offer opportunities for damage to the projectile surface during the manufacturing process.
All the methods heretofore known for significantly increasing the aerodynamic efficiency of hemispherical tip profile projectiles suffer from one or more of a number of disadvantages:
(a) Their manufacture involves casting, rolling, swaging, stamping, forming, forging, or machining processes requiring an ejection or release that presents an opportunity to damage the hemispherical tip surface of the projectile when it is removed from the manufacturing process, a situation that allows for significant aerodynamic differences between two similarly-produced projectiles.
(b) Their retention of a projectile's velocity customarily must be sacrificed in order to achieve improved aerodynamic stability and accuracy, or their stability and accuracy must be sacrificed in order to achieve improved velocity.
(c) Their manufacture is complex, often requiring hand finishing or complex methods to achieve a hollow or significantly hollow projectile through which a significant amount of air can pass undisturbed—these methods are not easily adapted to assembly-line manufacturing.
(d) If one uses a hollow or essentially hollow projectile in a near-sonic or supersonic application, the pressures within the hollow or essentially hollow projectile are likely to significantly disturb the projectile's flight, harm its accuracy, and jeopardize its velocity retention.
(e) They generally offer poor performance across a range of speeds, optimizing the design's aerodynamics around a small range of the speeds a projectile might encounter while experiencing only either supersonic or subsonic flight.
(f) Projectiles with improved aerodynamics generally are easily distinguished from regular munitions in terms of appearance or physical characteristics, making their use in place of regular munitions potentially difficult if accessories, magazines, extractors, and other firearm-related items are not designed with a particular type of aerodynamically-improved projectile in mind.
(g) Their manufacture often involves special casings or special “brass” designs that are not interchangeable with regular munitions of the same caliber.
(h) Ammunition designed with aerodynamic advantages often does not lend itself to backward-compatibility with earlier firearms designs including revolvers, pistols, machine pistols, and other firearms—many designs, though they may offer aerodynamic advantages, are sufficiently different in shape or mass to cause feed malfunctions or failure-to-fire malfunctions in firearms not designed with the peculiarities of the particular ammunition in mind.
(i) The use of lead and other substances of measurable toxicity in the manufacture of either cores or jackets of ammunition poses potential environmental and health risks.
Thus, improvements in the aerodynamic performance of ammunition, missiles and similar projectiles are desired, and these are now provided by the present invention.